Apparatuses and methods for maskless mesoscale material deposition

ABSTRACT

Apparatuses and processes for maskless deposition of electronic and biological materials. The process is capable of direct deposition of features with linewidths varying from the micron range up to a fraction of a millimeter, and may be used to deposit features on substrates with damage thresholds near 100° C. Deposition and subsequent processing may be carried out under ambient conditions, eliminating the need for a vacuum atmosphere. The process may also be performed in an inert gas environment. Deposition of and subsequent laser post processing produces linewidths as low as 1 micron, with sub-micron edge definition. The apparatus nozzle has a large working distance—the orifice to substrate distance may be several millimeters—and direct write onto non-planar surfaces is possible.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/349,279, entitled “Apparatuses And Method ForMaskless Mesoscale Material Deposition”, filed on Jan. 6, 2009, whichapplication is a divisional application of U.S. patent application Ser.No. 11/317,457, entitled “Apparatuses And Method For Maskless MesoscaleMaterial Deposition”, to Michael J. Renn, et al., filed on Dec. 22,2005, now U.S. Pat. No. 7,485,345, which is a divisional application ofU.S. patent application Ser. No. 10/346,935, entitled “Apparatuses AndMethod For Maskless Mesoscale Material Deposition”, to Michael J. Renn,et al., filed on Jan. 17, 2003, now U.S. Pat. No. 7,045,015, which is acontinuation-in-part application of the following U.S. patentapplications:

U.S. patent application Ser. No. 09/574,955, entitled “Laser-GuidedManipulation of Non-Atomic Particles”, to Michael J. Renn, et al., filedon May 19, 2000, now U.S. Pat. No. 6,823,124, which was a continuationapplication of U.S. patent application Ser. No. 09/408,621, entitled“Laser-Guided Manipulation of Non-Atomic Particles”, to Michael J. Renn,et al., filed on Sep. 30, 1999, now abandoned, which claimed the benefitof U.S. Provisional Patent Application Ser. No. 60/102,418, entitled“Direct-Writing of Materials by Laser Guidance”, to Michael J. Renn, etal., filed on Sep. 30, 1998;

U.S. patent application Ser. No. 09/584,997, entitled “Particle GuidanceSystem”, to Michael J. Renn, filed on Jun. 1, 2000, now U.S. Pat. No.6,636,676, which was a continuation-in-part application of U.S. patentapplication Ser. No. 09/574,955;

U.S. patent application Ser. No. 10/060,960, entitled “Direct Write™System”, to Michael J. Renn, filed on Jan. 30, 2002, now abandoned,which was a continuation-in-part application of U.S. patent applicationSer. Nos. 09/584,997 and 09/574,955; and

U.S. patent application Ser. No. 10/072,605, entitled “Direct Write™System”, to Michael J. Renn, filed on Feb. 5, 2002, now U.S. Pat. No.7,108,894, which was a continuation-in-part application of U.S. patentapplication Ser. Nos. 09/584,997 and 09/574,955;

and the specifications and claims of all of the preceding references areincorporated herein by reference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms as provided for by the terms of Contract No.N00014-99-C-0243 awarded by the U.S. Department of Defense.

FIELD OF THE INVENTION

The present invention relates generally to the field of direct writedeposition.

BACKGROUND OF THE INVENTION

The present invention relates to maskless, non-contact printing ofelectronic materials onto planar or non-planar surfaces. The inventionmay also be used to print electronic materials on low-temperature orhigh-temperature materials, and is performed without the need for aninert atmosphere. It is also capable of deposition of micron-sizefeatures.

DESCRIPTION OF THE PRIOR ART

Various techniques may be used for deposition of electronic materials,however thick film and thin film processing are the two dominant methodsused to pattern microelectronic circuits. Recently, ink jetting ofconductive polymers has also been used for microelectronic patterningapplications. Thick film and thin film processes for deposition ofelectronic structures are well-developed, but have limitations due tohigh processing temperatures or the need for expensive masks and vacuumchambers. Ink jetted conductive polymers have resistivities that areapproximately six orders of magnitude higher than bulk metals. Thus, thehigh resistivity of ink jetted conductive polymers places limitations onmicroelectronic applications. One jetting technique disclosed in U.S.Pat. Nos. 5,772,106 and 6,015,083 use principles similar to those usedin ink jetting to dispense low-melting temperature metal alloys, i.e.solder. The minimum feature size attainable with this method is reportedto be 25 microns. No mention, however, of deposition of pure metals onlow-temperature substrates is mentioned. U.S. Pat. Nos. 4,019,188 and6,258,733 describe methods for deposition of thin films from aerosolizedliquids. U.S. Pat. No. 5,378,505 describes laser direct write ofconductive metal deposits onto dielectric surfaces. Metal precursorswere dropped or spin-coated onto alumina or glass substrates anddecomposed using a continuous wave laser. The Maskless MesoscaleMaterial Deposition (M³D™) apparatus, on the other hand, provides amethod for the direct write of fine features of electronic materialsonto low-temperature or high-temperature substrates. The as-depositedline features may be as small as 10 microns, and may be treatedthermally or treated using laser radiation. The M³D™ process depositsliquid molecular precursors or precursors with particle inclusions, anduses a subsequent processing step that converts the deposit to thedesired state. The precursor viscosity may range from approximately 1 to1000 centiPoises (cP), as opposed to ink jetted solutions, which aretypically confined to around 10 cP. The M³D™ process may also depositaerosolized materials onto many substrates with damage thresholds as lowas 100° C., and is a maskless process that can run under ambient andinert environmental conditions.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a precision aerosoljetter for high resolution, maskless, mesoscale material deposition ofliquid and particle suspensions in patterns. It is another object toprovide a precision aerosol jetter that deposits electronic andbiological materials with patterns in the range from about 10 microns toas large as several millimeters, while being relatively free of cloggingand depositing on the orifice walls with the use of a sheath gas. It isanother object to provide a precision aerosol jetter that usesaerodynamic focusing to deposit a pattern onto a planar or non-planarsubstrate without the use of masks. It is a further object to providepost-processing treatment of the substrate thermally or photochemicallyto achieve physical and/or electrical properties near that of a bulkmaterial.

These, and other objects, are achieved by the present invention, whichprovides a precision aerosol jetter wherein an aerosolized liquidmolecular precursor, particle suspension, or a combination of both isdelivered to a flowhead via a carrier gas. The aerosolized precursorcombined with the carrier gas forms an aerosol stream. The carrier gasis controlled by an aerosol carrier gas flowrate. A virtual impactor maybe used to reduce the carrier gas flowrate. The virtual impactor may becomposed of one or many stages. The removal of the carrier gas in thismanner concentrates the aerosolized mist.

A heating assembly may be used to evaporate the aerosolized mist. Apreheat temperature control is used to change the heating assembly'stemperature. The aerosolized mist may also be humidified to keep it fromdrying out. This is accomplished by introducing water droplets, vapor,or other non-water based material into the carrier gas flow. Thisprocess is useful for keeping biological materials alive.

The resulting aerosol stream enters the flowhead and is collimated bypassing through a millimeter-size orifice. An annular sheath gascomposed of compressed air or an inert gas, both with modified watervapor content, enters the flowhead through multiple ports to form aco-axial flow with the aerosol stream. The sheath gas serves to form aboundary layer that prevents depositing of the particles in the aerosolstream onto the orifice wall. The aerosol stream emerges from theflowhead nozzle onto a substrate with droplets or particles contained bythe sheath gas.

The aerosol stream may then pass through a processing laser with afocusing head. An acousto-optic modulator controls beam shuttering.

A shutter is placed between the flowhead orifice and the substrate inorder to achieve patterning. The substrate is attached to acomputer-controlled platen that rests on X-Y linear stages. A substratetemperature control is used to change the substrate's temperature. Thesubstrate may also be composed of biocompatible material. Patterning iscreated by translating the flowhead under computer control whilemaintaining a fixed substrate, or by translating the substrate whilemaintaining a fixed flowhead.

A control module is used to modulate and control the automation ofprocess parameters such as aerosol carrier gas flowrate, annular sheathgas flowrate, preheat temperature, and substrate temperature. A motioncontrol module is used to modulate and control the X-Y linear stages,Z-axis, material shutter, and laser shutter.

A BRIEF DESCRIPTION OF THE DRAWINGS

1. FIG. 1 is schematic of the M³D™ apparatus.

2. FIG. 2 is a side view of the M³D™ flowhead.

3. FIG. 3 a is a drawing showing flow-control of a single stage virtualimpactor.

4. FIG. 3 b is a drawing showing flow-control of a multi-stage virtualimpactor.

5. FIG. 4 shows a silver redistribution circuit deposited on Kapton™,with lines that are approximately 35 microns wide.

6. FIG. 5 shows a laser decomposed RF filter circuit on barium titanate,in which VMTool is used to pattern and decompose a silver film depositedon a barium titanate substrate.

7. FIG. 6 is a schematic representation of a three-layer direct writeinductor.

A DETAILED DESCRIPTION OF THE PREFERRED AND ALTERNATIVE EMBODIMENTSGeneral Description

The present invention relates to apparatuses and methods forhigh-resolution, maskless deposition of liquid and particle suspensionsusing aerodynamic focusing. An aerosol stream is focused and depositedonto any planar or non-planar substrate, forming a pattern that isthermally or photochemically processed to achieve physical and/orelectrical properties near that of the corresponding bulk material. Theprocess is termed M³D™, Maskless Mesoscale Material Deposition, and isused to deposit aerosolized materials with linewidths that are an orderof magnitude smaller than lines deposited with conventional thick filmprocesses. Deposition is performed without the use of masks. The termmesoscale refers to sizes from approximately 10 microns to 1 millimeter,and covers the range between geometries deposited with conventional thinfilm and thick film processes. Furthermore, with post-processing lasertreatment, the M³D™ process is capable of defining lines as small as 1micron in width.

The present invention comprises an apparatus comprising preferably anatomizer for atomizing liquid and particle suspensions, directing,preferably a lower module for directing and focusing the resultingaerosol stream, a control module for automated control of processparameters, a laser delivery module that delivers laser light through anoptical fiber, and a motion control module that drives a set of X-Ytranslation stages. The apparatus is functional using only the lowermodule. The laser module adds the additional capability of curingmaterials on low temperature substrates. Aerosolization is accomplishedby a number of methods, including using an ultrasonic transducer or apneumatic nebulizer. The aerosol stream is focused using the M³D™flowhead, which forms an annular, co-axial flow between the aerosolstream and a sheath gas stream. The co-axial flow exits the flowheadthrough a nozzle directed at the substrate. The M³D™ flowhead is capableof focusing an aerosol stream to as small as one-tenth the size of thenozzle orifice. Patterning is accomplished by attaching the substrate toa computer-controlled platen. Alternatively, in a second configuration,the flowhead is translated under computer control while the substrateposition remains fixed. The aerosolized fluid used in the M³D™ processconsists of any liquid source material including, but not limited to,liquid molecular precursors for a particular material, particulatesuspensions, or some combination of precursor and particulates.

Another embodiment of the present invention is the Direct WriteBiologics (DWB™) process. The DWB™ process is an extension of the M³D™process wherein biological materials are deposited in mesoscale patternson a variety of biocompatible substrates. Like the M³D™ process, anaerosol is first generated, and materials are deposited onto the desiredsubstrate surface. Stock solutions containing biological molecules suchas functional catalytic peptides, extracellular matrix (ECM) andfluorescent proteins, enzymes, or oligonucleotides have all demonstratedpost-process functionality. A wide range of biological materials havebeen deposited using the direct-write method. Indeed, biomaterialaerosols containing biologically active molecules can be deposited intopatterned structures to generate engineered substrates. In addition,possible whole cell deposition applications include embeddedarchitecture tissue constructs and tissue-based biosensor development.

Applications of the M³D™ process include, but are not limited to, directwrite of circuits and devices for electronic applications, as well asthe direct write of materials for biological applications.

Preferred Embodiment 1. Aerosolization

FIG. 1 shows the preferred M³D™ apparatus. Like reference numerals areused to describe the same elements throughout the various figures inorder to create parity and for convenience of illustration. The M³D™process begins with the aerosolization of a solution of a liquidmolecular precursor or suspension of particles. The solution may also bea combination of a liquid molecular precursor and particles. As by wayof example, and not intended as limiting, precursor solutions may beatomized using an ultrasonic transducer or pneumatic nebulizer 14,however ultrasonic aerosolization is limited to solutions withviscosities of approximately 1-10 cP. The fluid properties and the finalmaterial and electrical properties of the deposit are dependent on theprecursor chemistry. Aerosolization of most particle suspensions isperformed using pneumatics, however ultrasonic aerosolization may beused for particle suspensions consisting of either small or low-densityparticles. In this case, the solid particles may be suspended in wateror an organic solvent and additives that maintain the suspension. Fluidswith viscosities from approximately 1 to 1000 cP may be atomizedpneumatically. These two methods allow for generation of droplets ordroplet/particles with sizes typically in the 1-5 micron size range.

2. Flow Development and Deposition

Aerosol Delivery, Drying, and Humidification

The mist produced in the aerosolization process is delivered to adeposition flowhead 22 using a carrier gas. The carrier gas is mostcommonly compressed air or an inert gas, where one or both may contain amodified solvent vapor content. The carrier gas flowrate is controlledby a carrier gas controller 10. The aerosol may be modified whiletransiting through a heating assembly 18. The heating assembly 18 isused to evaporate the precursor solvent and additives or theparticle-suspending medium. This evaporation allows for the modificationof the fluid properties of the aerosol for optimum deposition. Partialevaporation of the solvent increases the viscosity of the depositedfluid. This increased viscosity allows for greater control of thelateral spreading of the deposit as it contacts the substrate 28. Apreheat temperature control 20 is used to change the heating assembly'stemperature. In contrast, in some cases, humidifying the carrier gas isnecessary to prevent drying of the aerosol stream. Humidification of thesheath airflow is accomplished by introducing aerosolized waterdroplets, vapor, or other non-water based material into the flow. Thismethod is used in the case where the solvent used for a particularprecursor material would otherwise completely evaporate before theaerosol reaches the substrate 28.

General Description of Flow-Guidance

FIG. 2 shows the preferred M³D™ flowhead. In the flow guidance process,the aerosol stream enters through ports mounted on the flowhead 22 andis directed towards the orifice 38. The mass throughput is controlled bythe aerosol carrier gas flowrate. Inside the flowhead 22, the aerosolstream is initially collimated by passing through a millimeter-sizeorifice. The emergent particle stream is then combined with an annularsheath gas. The sheath gas is most commonly compressed air or an inertgas, where one or both may contain a modified solvent vapor content. Thesheath gas enters through the sheath air inlet 36 below the aerosolinlet 34 and forms a co-axial flow with the aerosol stream. The sheathgas is controlled by a sheath gas controller 12. The combined streamsexit the chamber through an orifice 38 directed at the substrate 28.This co-axial flow focuses the aerosol stream onto the substrate 28 andallows for deposition of features with dimensions as small as 10microns. The purpose of the sheath gas is to form a boundary layer thatboth focuses the particle stream and prevents particles from depositingonto the orifice wall. This shielding effect minimizes clogging of theorifices. The diameter of the emerging stream (and therefore thelinewidth of the deposit) is controlled by the orifice size, the ratioof sheath gas flow rate to carrier gas flow rate, and the spacingbetween the orifice and the substrate. In a typical configuration, thesubstrate 28 is attached to a platen that moves in two orthogonaldirections under computer control via X-Y linear stages 26, so thatintricate geometries may be deposited. Another configuration allows forthe deposition flowhead to move in two orthogonal directions whilemaintaining the substrate in a fixed position. The process also allowsfor the deposition of three-dimensional structures.

Virtual Impaction

Many atomization processes require a higher carrier gas flow rate thanthe flowhead can accept. In these cases, a virtual impactor is used inthe M³D™ process to reduce the flowrate of the carrier gas, withoutappreciable loss of particles or droplets. The number of stages used inthe virtual impactor may vary depending on the amount of excess carriergas that must be removed. By way of example, FIG. 3 a shows a singlestage virtual impactor.

A single stage virtual impactor comprises a nozzle 40, a large chamber42 with an exhaust port 44 and a collection probe 46. The nozzle 40 andcollection probe 46 are opposed to each other within the chamber 42. Aparticulate laden gas stream, referred to as the total flow, Q₀ isaccelerated through the nozzle 40 into the chamber 42. The jet ofparticulate laden gas penetrates the collection probe 46, however mostof the gas flow reverses direction and exits the collection probe 46back into the chamber 42. This flow is referred to as the major flow andis exhausted. The flow that remains in the collection probe 46 isreferred to as the minor flow and is directed downstream for furtherprocessing. Particles having sufficient momentum will continue to followa forward trajectory through the collection probe 46 and will be carriedby the minor flow. Particles with insufficient momentum will beexhausted with the major flow. Momentum of the particles is controlledby the particle size and density, the gas kinematic properties, and thejet velocity. The particle size at which particles have just enoughmomentum to enter the collection probe 46 is referred to as thecut-point of the impactor. In order for the virtual impactor to functionproperly, the exhaust gas must be removed from the chamber 42 at aspecific flowrate. This may be accomplished by feeding the exhaust gasthrough a flow control device such as a mass flow controller. In theevent that ambient conditions do not provide a sufficient pressure dropto achieve the flowrates required for proper operation, a vacuum pumpmay be used.

In the present invention, the particles entrained in the gas streamconsist of droplets, generally in the size range of 1-5 microns althoughdroplets smaller than 1 micron and as large as 50 microns may be used.Particles larger than the cut-point enter the collection probe 46 andremain in the process. These are directed into other devices downstreamof the impactor. Droplets smaller than the cut-point remain in thestripped excess gas and are no longer part of the process. These may beexhausted to the atmosphere through the exhaust port 44, filtered toavoid damaging flow control devices, or collected for reuse.

The efficiency of the virtual impactor is determined by the amount ofaerosol that remains in the minor flow and is not stripped out in themajor flow along with excess gas or physically impacted out in thevirtual impactor. Close geometrical control of the impactor can improvethe efficiency, as can control of the particle size distribution in theaerosol. By shifting the particle size distribution above the cut-pointof the impactor, all the particles will remain in process, minimizingboth waste and clogging. Another option exists to intentionally designan impactor stage to strip off particles below a certain size range,such that only particles above a certain size are presented to thedownstream processes. Since the deposition is a physical impactionprocess, it may be advantageous to present only droplets of a certainsize to the substrate. For example, resolution may be improved bydepositing only 5 micron sized droplets. Other examples where it may beadvantageous to deposit only certain sized droplets include via filling.

In the event that a single stage of virtual impaction is insufficient toremove enough excess carrier gas, multiple stages of impaction may beemployed. FIG. 3 b shows a multi-stage virtual impactor. In this case,the output from the collection probe 46 of the first virtual impactor isdirected into the nozzle 40 of the second impactor and so on, for therequired number of stages.

Shuttering

A computer-controlled material shutter 25 is placed between the flowheadorifice and the substrate 28. FIG. 1 shows the shutter. The shutter 25functions to interrupt the flow of material to the substrate 28 so thatpatterning is accomplished.

Temperature Control

A substrate temperature control 30 is used to change the temperature ofthe substrate 28, as shown in FIG. 1.

3. Control Module

The M³D™ control module provides automated control of process parametersand process monitoring. The process parameters include the aerosol andsheath gas flowrates, the aerosol preheat temperature and the substratetemperature. The control module may be operated as a stand-alone unitvia manual input on the front panel, or remotely via communication witha host computer. Remote operation via a host computer is preferable forcoordinating the deposition system with the other components of the M³D™system.

4. Laser Delivery Module

The M³D™ apparatus uses a commercially available laser 24. Deposits aretypically processed using a continuous wavelength frequency-doubledNd:YAG laser, however processing may be accomplished with a variety oflasers, granted that the deposit is absorbing at the laser wavelength.The laser delivery module comprising a laser, a mechanical shutter, anacousto-optic modulator, delivery optics, and a focusing head. Themechanical shutter is used to rapidly turn the laser on and off incoordination with the motion control system. The acousto-optic modulatoris used for rapid dynamic power control, which optionally may also becoordinated with motion. The delivery optics may be either an opticalfiber and associated launch optics or mirrors. The laser delivery moduleis controlled via communication with the host computer.

5. Motion Control Module

The motion control module consists of a motion control card, an I/Ointerface, X-Y linear stages 26 for moving either the substrate or thedeposition system, a z-axis for positioning the deposition system abovethe substrate and amplifiers for driving the stages. The I/O interface,amplifiers and associated power supplies are housed in an external, rackmountable enclosure. The motion control card typically is installed inthe host computer and is connected to the I/O interface via a specialcable. The I/O interface consists of analog outputs to the driveamplifiers and discrete outputs for actuating the material and lasershutters. Control of these components is handled by the motion controlmodule rather than their respective control modules so that the timingof shuttering events can be coordinated with motion.

6. Materials

The M³D™ process has been used to deposit a range of materials,including electronic and biological materials. Aerosolization of thesematerials may be from liquid precursor inks, particulate suspensions orcombinations of both precursors and particulates. Aerosolization offluids from roughly 1 to 1000 cP is possible. Biological materials maybe deposited without loss of functionality. The materials developedspecifically for the M³D™ process have low processing temperatures (150°C. to 200° C.), may be written with linewidths as small as 10 microns,have excellent adhesion to plastic, ceramic, and glass substrates, andhave electrical properties near that of the bulk material. Electronicmaterials may be processed thermally, or using laser treatment.

The M³D™ process can also be used in multiple material deposition. Forexample, the M³D™ process can be used to deposit different materialswithin a single layer, or it can be used to deposit different materialsonto different layers.

Metals

The M³D™ process can be used to deposit metals such as silver, platinum,palladium, rhodium, copper, gold, and silver/palladium andplatinum/rhodium alloys. In the most general case, metal structures areformed from aerosolized liquid precursors for the desired metals,however precursors are also formulated with nanometer-size metalparticles. The inclusion of nanometer-sized metal particles isbeneficial to many aspects of the system, including, but not limited to,optimization of fluid properties, improved densification and finalproperties of the deposit. A particular strength of theapparatus/material combination is that maskless deposition ontosubstrates with damage thresholds as low as 150° C. may be achieved.Optimized fluid properties and apparatus parameters also allow fordeposition with linewidths as small as 10 microns. Subsequent laserprocessing may be used to define features with linewidths as small as 1micron. The precursor formulations also provide good adhesion to Kapton™(as shown in FIG. 4), glass, barium titanate (as shown in FIG. 5), andvarious plastics.

The M³D™ process can be used to direct write metal traces withlinewidths as small as 1 micron, and as large as 100 microns. Electricalinterconnects have been written with linewidths from 10 microns to 250microns. In general, the resistivity of the traces is from 2 to 5 timesthat of the bulk metal insulators. A silver/glass formulation has beenused as a low-ohmic resistive system, capable of producing traces withresistances from approximately 1 ohm to 1 kohm. The formulation consistsof a silver/palladium precursor and a suspension of fumed silicaparticles. The process can be used to write resistor terminations,interdigitated capacitors, inductive coils, and spiral antennas andpatch antennas. The M³D™ process can also be used to deposit reflectivemetals with very low surface roughness for micro-mirror applications.

Ceramics

The M³D™ process can be used to direct write ceramics, includinginsulators, mid- and high-k dielectrics, resistor materials andferrites. Source materials have been precursors, colloidal suspensionsand mixtures of the two. Low-k dielectric materials such as glass havebeen deposited both for dielectric layers in capacitor applications, aswell as insulation or passivation layers. High-k dielectrics such asbarium titanate can be deposited for capacitor applications, ruthenateshave been deposited to form resistors and manganeses zinc ferrites havebeen deposited to form inductor cores.

A broad range of ceramics may be deposited and fired conventionally.However, densification on low temperature substrates can only beachieved for materials that can be densified either at temperaturesbelow the damage threshold of the substrate or by laser treatment.

Polymers

The M³D™ process can be used to directly write polymeric materials. Theliquid source materials can be monomers, solutions, suspensions, or anycombination of these. Examples of polymers that have been depositedinclude polyimide, polyurethane and UV curable epoxies. The finaltreatment of the deposit is dependant on the specific polymer, but mayinclude thermal heating, laser processing or exposure to UV. Polymericdeposits have been used as low-k dielectrics for capacitors and overcoatdielectrics for electrical and environmental insulation.

The M³D™ process can also be used to deposit traditional electronicmaterials onto polymers, such as polyimide, polyetheretherketone (PEEK),Teflon™, and polyester, at temperatures below those required to causedamage.

Resistive Lines

Resistive traces with resistances spanning six orders of magnitude canbe deposited using the M³D™ process. A silver/glass formulation has beenused as a low-ohmic system, capable of producing traces with resistancesfrom approximately 1 ohm to 1 kohm. The formulation consists of asilver/palladium precursor and a suspension of fumed silica particles. Amid to high ohmic formulation has been developed using a suspension ofruthenium oxide particles in dimethylacetimide. Resistances from roughly50 ohm to 1 Mohm are possible with the Ruthenium Oxide system.

Inductive Deposits

Inductive materials may also be deposited using the M³D™ process. Azinc/manganese ferrite powder combined with a low-melting temperatureglass powder has been atomized and deposited onto Kapton™. Both thermaland laser processes can be used to sinter the powder. Both processesresulted in a dense well-adhered ferrite layer.

Other Materials

The M³D™ process can deposit a myriad of other materials for variousprocesses. For example, the M³D™ process can be used to depositsacrificial and resist materials for subsequent processing of asubstrate, such as in chemical etching. It can also deposit sacrificialmaterials to form support structures onto or into a structure usingadditional materials. The M³D™ process can deposit solvent and etchingchemicals to directly texture a substrate. The M³D™ process can also beused to deposit dissimilar materials in the same location for furtherprocessing to form a multi-phase mixture, alloy, or compound, and it candeposit dissimilar materials to form structures with a compositionalgradient. The M³D™ process can create porosity or channels in structuresby depositing fugitive materials for later removal. The M³D™ process canalso deposit materials, which are structural in nature.

7. Heat Treatment

In the M³D™ process either thermal treatment or laser treatment may beused to process deposited materials to the desired state. In the case ofmetal precursors, dense metal lines may be formed with thermaldecomposition temperatures as low as 150° C. For precursor-basedmaterials, thermal treatment is used to raise the temperature of thedeposit to its decomposition or curing temperature. In these processes,a chemical decomposition or crosslinking takes place as a result of theinput of thermal energy, such that the precursor changes its molecularstate, resulting in the desired material plus some effluents. An exampleof a chemical decomposition of a molecular precursor to a metal is thatof the reaction of silver nitrate, a metal salt, to form silver plusnitrogen, oxygen, and nitrogen/oxygen compounds.

In the curing process, heat is added to the deposit until the effluentsare driven off and polymerization takes place. Chemical decompositionhas also been accomplished using laser radiation as the heat source. Inthis case, the precursor or precursor/particle combination is formulatedso that the fluid is absorbing at the laser wavelength. The highabsorption coefficient at the laser wavelength allows for very localizedheating of the deposit, which in turn may be used to produce finedeposits (as small as 1 micron for a frequency-doubled Nd: YAG laser)with no damage to the substrate. The M³D™ process has been used todeposit and laser process silver on an FR4 substrate, which has a damagethreshold of less than 200° C.

In the deposition of ceramics and other refractory powders, lasersintering is used to soften low-melting temperature particles used tobind the refractory powder. In this process the laser is scanned overthe deposit and absorbed by the glass or the powder, softening the glassto the point that adhesion takes place between particles and thesubstrate.

In the case of DWB™, thermal treatment is used to incubate depositedsamples. The goal of incubation is to produce a desired chemicalreaction, such as the development of enzyme activity.

8. Direct Write of Biological Materials

Cell patterning by flow-guided direct writing may revolutionize cellpatterning technology by allowing for precise cellular micro-patterningand addition of biologically active adhesion or pathway signalingbiomolecules. This is the most general advantage and arguably the mostrevolutionary component of the DWB™ technology. The direct-write methodcan be used to guide and deposit 0.02 μm to 20 μm diameter biologicalparticles onto substrate surfaces. The range of biological materialsthat can be deposited is extremely broad, and includes polymers,peptides, viruses, proteinaceous enzymes and ECM biomolecules, as wellas whole bacterial, yeast, and mammalian cell suspensions.

9. Products and Applications

Two examples of devices that demonstrate the capabilities of the M³D™process are described. The first device is a manganese-zinc ferriteinductor written on alumina, as shown in FIG. 6. This devicedemonstrates deposition of silver precursor plus laser processing of thedeposit. The silver precursor is ultrasonically atomized from liquidprecursor solution, In addition, a ferrite and glass particle suspensionis pneumatically atomized, deposited, and laser densified. The silverdeposition illustrates the capability to deposit over a non-planarsurface. The second device is a silver spiral on Kapton™, demonstratingfine feature size and direct write of silver onto a low-temperaturesubstrate.

Direct Write Inductor

A three-dimensional ferrite-core inductor has been built using the M³D™apparatus and process. FIG. 6 shows a three-layer direct write inductor.The first step of the inductor fabrication is the deposition of parallellines of silver precursor 56 onto an alumina substrate. The lines areapproximately 100 microns wide, 1 micron thick and 1000 microns inlength. The lines are laser treated to form dense, conductive silverwires. These wires are one-half of the conductive traces that willeventually wrap around a ferrite core. Silver contact pads 58 a-b (1000micron square) are also added in the first layer.

The second step is to create the inductor core 60 by depositing amixture of Manganese-Zinc Ferrite powder and low melting temperatureglass over the conductive lines. Laser sintering is used to densify theferrite/glass deposit; the glass flows around the ferrite particles andforms a dense, connected solid after cooling. The ferrite depositionstep is repeated several times to buildup the deposit to about 150microns. The ferrite line lengths are about 1500 mm long. A typicalprofile of the ferrite layer is shown in FIG. 6.

The final step is to write conductive traces over the ferrite layer andconnect them to the underlying traces to form the inductor coil 62.Since the flowguide head standoff distance is several mm, depositionover a mm-sized non-planar surface is possible. The resistance of atypical coil generated using this method is on the order of severalohms. The inductance is 7 micro henries and the Q value is 4.2 @ 1 MHz.

Direct Write Spiral

The M³D™ process has been used to form a direct write spiral, whichshows the line definition and feature size capabilities of the process.The spiral lines are 35 microns in diameter on a 60-micron pitch. Theoverall diameter of the coil is 2.0 mm. The start material is silver inkthat was deposited and then treated at 200° C. to chemically decomposethe precursors and densify the deposit. In depositing this pattern, thesubstrate was translated beneath the deposition head at a speed of 10mm/s

Other Applications

The M³D™ process can be used to perform a plethora of otherapplications. It can perform layerwise deposition of materials to formfunctional devices, such as multilayer capacitors, sensors, andterminated resistors. It has the capacity to deposit multiple materialsto form structures, such as interconnects, resistors, inductors,capacitors, thermocouples, and heaters, on a single layer. The M³D™process can deposit multilayer structures consisting of conductorpatterns and dielectric insulating layers, in which the conductorpatterns may be electrically connected by conducting vias. It candeposit a passivation material to protect or insulate electronicstructures. It can deposit overlay deposits for the purpose of “additivetrimming” of a circuit element, such as adding material to a resistor toalter its value. The M³D™ process can also deposit these overlaydeposits on top of existing structures, which is difficult to achievewith screen printing.

In the area of novel microelectronic applications, the M³D™ process candeposit materials between preexisting features to alter a circuit orrepair broken segments. It can deposit metal films with taperedlinewidths for devices, such as a stripline antennae. It can alsodeposit material to form “bumps” for chip attachment. The M³D™ processcan deposit adhesive materials to form dots or lines for application tobonding multiple substrates and devices. The M³D™ process can alsodeposit materials into underfill regions, in which the deposit is pulledinto the underfill region by capillary forces.

In a printing application, the M³D™ process can depositthree-dimensional patterns to fabricate a master stamp. It can alsodeposit colored pigments (e.g. red, green, blue) to generate highresolution colored deposits.

The M³D™ process may also be used in several optoelectronicapplications, and can deposit transparent polymers into lines and dotsto serve as lenses and optical conductors. It can also depositrepetitive structures, such as lines and dots, to refract or reflectlight and to serve as diffractive optical elements, such as diffractiongratings or photonic bandgaps. It can deposit metal and dielectric filmswith tapered film thickness, in which the films can serve as opticalphase retarders that can encode holographic information into lightbeams. Examples of this are phase shift masks, diffractive opticalelements, and holograms. The M³D™ process can also deposit metal andopaque films of variable thickness for controlled reflection andabsorption of light. Such a process can be used to make high-resolutionportraits.

The M³D™ process can deposit materials that form a thermal or chemicalbarrier to the underlying substrate. It can deposit materials that havea primary function of bearing a load, reducing friction between movingparts, or increasing friction between moving parts. It can also depositmaterials used to form memory devices. Further, the M³D™ process candeposit materials that form a logic gate.

10. Direct Write Biological (DWB™) Applications

The DWB™ initiative may be applied to material deposition applicationsincluding biosensor rapid prototyping and microfabrication, microarraybio-chip manufacturing, bioinspired electroactive polymer conceptdevelopment (ambient temperature bio-production of electroniccircuitry), and various additive biomaterial processes for hybridBioMEMS and Bio-Optics. Moreover, the ability to deposit electronic andbiologically viable or active materials with mesoscale accuracy haspotential to advance these application areas.

The M³D™ process can also be used to deposit multiple materials in adot-array geometry for biological applications, such as for protein andDNA arrays. It can deposit passivation material to protect or insulatebiological structures. It can also deposit an overlay material onto anexisting structure that selectively allows migration of certain chemicalor biological species to the existing structure while preventing thepassage of others. Further, the M³D™ process can deposit materialscontaining a chemical or biological species that is released as afunction of time or an internal or external stimulus.

11. Topological Deposition

The M³D™ process can perform various topological depositions. Forexample, it can deposit spots, lines, filled areas, or three-dimensionalshapes. It has the capability to perform conformal deposition overcurved surfaces and steps. It can deposit into channels or trenches, oronto the sides of channel walls. It can deposit into via holes as smallas 25 microns.

The M³D™ process can deposit across multiple substrate materials. It candeposit longitudinally or circumferentially around cylindrically-shapedobjects. It can also deposit both internally or externally ontogeometrical shapes having flat faces that meet as sharp corners, such ascubes. The M³D™ process can deposit onto previously deposited material.It can also deposit films with variable layer thickness. Further, theM³D™ process can deposit films or lines with variable widths.

CONCLUSION

Although the present invention has been described in detail withreference to particular preferred and alternative embodiments, personspossessing ordinary skill in the art to which this invention pertainswill appreciate that various modifications and enhancements may be madewithout departing from the spirit and scope of the Claims that follow.The various configurations that have been disclosed above are intendedto educate the reader about preferred and alternative embodiments, andare not intended to constrain the limits of the invention or the scopeof the Claims. The List of Reference Characters which follows isintended to provide the reader with a convenient means of identifyingelements of the invention in the Specification and Drawings. This listis not intended to delineate or narrow the scope of the Claims.

LIST OF REFERENCE CHARACTERS FIG. 1

-   10 Carrier gas controller-   12 Sheath gas controller-   14 Pneumatic nebulizer/Ultrasonic atomizer-   16 Virtual impactor-   18 Heating assembly-   20 Preheat temperature control-   22 Flowhead-   24 Processing laser-   25 Shutter-   26 X-Y linear stages-   28 Substrate-   30 Substrate temperature control-   32 Computer

FIG. 2

-   34 Aerosol/carrier gas inlet-   36 Sheath air inlet-   38 Orifice

FIG. 3 a

-   40 Nozzle-   42 Chamber-   44 Exhaust port-   46 Collection probe

FIG. 3 b

-   No new reference numerals required.

FIG. 4

-   No reference numerals required.

FIG. 5

-   No reference numerals required.

FIG. 6

-   56 Parallel lines of silver precursor-   58 a-b Silver contact pads-   60 Inductor core-   62 Inductor coil

Although specific embodiments have been described and illustratedherein, it will be appreciated by those skilled in the art that anyarrangement, which is calculated to achieve the same purpose, may besubstituted for the specific embodiments shown. Therefore, thisapplication is intended to cover any adaptations or variations of thepresent invention. Therefore, it is manifestly intended that thisinvention only be limited by the following claims.

What is claimed is:
 1. A method for maskless material deposition of aliquid or liquid containing a particle suspension in a pattern on atarget, the method comprising: focusing an aerosol stream comprisingdroplets of the liquid; surrounding the aerosol stream with an annularsheath gas; subsequently passing the aerosol stream through no more thanone orifice; depositing the aerosol stream in a pattern onto a planar ornon-planar substrate without use of masks to form a deposit comprising afeature size of less than one millimeter; and processing the deposit sothat the deposit comprises physical and/or electrical properties nearthose of a bulk material.
 2. The method as claimed in claim 1, whereinthe liquid is a liquid molecular precursor or a particle suspension. 3.The method as claimed in claim 2 further comprising using ultrasonicaerosolization for particle suspensions comprising either or both ofhigh-density nanometer-sized particles ranging from 4 to 21 g/cm³ andlow-density micron-sized particles on the order of 2 g/cm³ or less. 4.The method as claimed in claim 1, further comprising the step ofatomizing the liquid using an ultrasonic transducer or a pneumaticnebulizer, thereby forming said droplets.
 5. The method as claimed inclaim 1, wherein the liquid has a viscosity of approximately 1-10 cP. 6.The method as claimed in claim 1, wherein the aerosol stream includesbiological materials selected from the group consisting of functionalcatalytic peptides, extracellular matrix and fluorescent proteins,enzymes, and oligonucleotides.
 7. The method as claimed in claim 1,wherein the aerosol stream is delivered to a deposition head via acarrier gas.
 8. The method as claimed in claim 7, wherein the carriergas and/or the sheath gas is selected from the group consisting ofcompressed air, an inert gas, a solvent vapor, and a combinationthereof.
 9. The method as claimed in claim 7, further comprisinghumidifying the carrier gas and/or the annular sheath gas to prevent thedrying of the aerosol stream.
 10. The method as claimed in claim 9,wherein humidifying the carrier gas and/or the annular sheath gascomprises introducing aerosolized water droplets and/or water vapor intothe carrier gas flow, the sheath gas flow, and/or the aerosol stream.11. The method as claimed in claim 7, wherein a mass throughput of theaerosol stream is controlled by a flowrate of the carrier gas.
 12. Themethod as claimed in claim 11, further comprising concentrating theaerosol stream by partially removing of the carrier gas.
 13. The methodas claimed in claim 12, wherein the carrier gas is partially removed byone or more stages of a virtual impactor.
 14. The method as claimed inclaim 1 further comprising at least partially evaporating a solventand/or a suspending fluid, thereby modifying fluid properties of theaerosol stream.
 15. The method as claimed in claim 14, wherein at leastpartially evaporating a solvent and/or a suspending fluid increasesviscosity of the aerosol stream, thereby enabling greater control of alateral spreading of the deposit.
 16. The method as claimed in claim 1,wherein the annular sheath gas forms a co-axial flow with the aerosolstream.
 17. The method as claimed in claim 16, wherein the co-axial flowexits a flowhead through a nozzle comprising an orifice, the nozzledirected at the substrate.
 18. The method as claimed in claim 17,wherein the annular sheath gas forms a boundary layer that focuses theaerosol stream and/or prevents particles in the aerosol from depositingonto a surface of the orifice.
 19. The method as claimed in claim 18,wherein the co-axial flow is focused as small as a tenth of a size ofthe nozzle orifice.
 20. The method as claimed in claim 17, furthercomprising interrupting flow of the aerosol stream to the substrate byoperating a shutter disposed between the nozzle orifice and thesubstrate.
 21. The method as claimed in claim 20, further comprisingpatterning the deposit by operating the shutter and translating thenozzle relative to the substrate.
 22. The method as claimed in claim 21,wherein patterning features of the deposit range in scale fromapproximately 10 microns to as large as several millimeters.
 23. Themethod as claimed in claim 1, wherein processing the deposit comprisesraising a temperature of the deposit to a decomposition temperature,sintering temperature, or curing temperature of the deposit.
 24. Themethod as claimed in claim 23, wherein the deposit comprises a precursorand thermal treatment of the deposit causes a chemical decomposition orcrosslinking to occur in the deposit, thereby changing a molecular stateof the precursor.
 25. The method as claimed in claim 1, wherein thedeposit comprises one or more elements selected from the groupconsisting of an electrical interconnect; a resistor termination, aninterdigitated capacitor; an inductive core or coil; a spiral antenna; apatch antenna; a reflective metal for micro-mirror applications; adielectric layer for capacitor applications; an insulating orpassivating layer; an overcoat dielectric; patterned biological cells;one or more interconnects, resistors, inductors, capacitors,thermocouples, or heaters on a single layer; an overlay deposit; astructure deposited between preexisting features to alter a circuit orrepair a broken circuit element; a metal film comprising a taperedlinewidth; colored pigments; patterned transparent polymer; periodicoptical structures, variable thickness metal and/or opaque film; athermal or chemical barrier to the underlying substrate; a chemical orbiological species which is time released or released in response to acertain internal or external stimulus; and a film or line comprising avariable linewidth.
 26. The method of claim 25 wherein the depositcomprises one or more element selected from the group consisting of anelectrical interconnect comprising a linewidth between about 10 micronsand about 250 microns; a spiral antenna comprising silver and thesubstrate comprising Kapton™; an overlay deposit used for additivetrimming of a circuit element; an overlay deposit disposed on top of anexisting structure; a metal film comprising a tapered linewidth used fora stripline antenna; colored pigments comprising red, green, and bluepigments; colored pigments used in a high resolution display; apatterned transparent polymer comprising lines and or dots; a patternedtransparent polymer forming a lens or an optical conductor; periodicoptical structures refracting light; periodic optical structuresreflecting light; periodic optical structures forming a diffractiveoptical element; periodic optical structures forming a diffractiveoptical element comprising a diffraction grating; periodic opticalstructures forming a diffractive optical element comprising a photonicbandgap; a variable thickness metal film controlling reflection andabsorption of light; a variable thickness metal film used in ahigh-resolution portrait; a variable thickness opaque film controllingreflection and absorption of light; and a variable thickness opaque filmused in a high-resolution portrait.
 27. The method of claim 1 furthercomprising rapidly prototyping and/or microfabricating a biosensor. 28.The method of claim 1 wherein the aerosol stream is deposited in one ormore ways selected from the group consisting of into a channel ortrench, on the side of a channel wall or trench wall, conformally over acurved surface, conformally over a step, into a via hole, acrossmultiple substrate materials, and longitudinally or circumferentiallyaround a cylindrically-shaped object.
 29. The method as claimed in claim1, wherein the processing step comprises photochemically processing thedeposit.
 30. The method as claimed in claim 29, wherein the deposit isphotochemically processed by a laser.
 31. The method as claimed in claim1, wherein the substrate comprises a biocompatible material.